FIELD: chemistry.
SUBSTANCE: present invention relates to a method of producing an aqueous emulsion of modified polytetrafluoroethylene, a method of producing a fine powder of modified polytetrafluoroethylene and a method of producing a stretched porous body of modified polytetrafluoroethylene. Method of producing an aqueous emulsion of modified polytetrafluoroethylene is a method of producing an aqueous emulsion of non-molten particles of modified polytetrafluoroethylene, having an average primary particle diameter of 0.10–0.30 mcm, in which tetrafluoroethylene and perfluoroalkylethylene, represented by following formula (1), are subjected to emulsion polymerisation in an aqueous medium using a polymerisation initiator in the presence of a fluorinated anionic surfactant having LogPOW of 2.4 to 3.4, where fluorinated anionic surfactant is a fluorinated surfactant having 6 or 7 carbon atoms, 0 or 1 hydrogen atom, 0 or 1 to 4 oxygen atoms in form of ether groups, -COOA group, where A is H, NH4 or an alkali metal atom, and the remaining atoms are fluorine atoms, and said fluorinated anionic surfactant is used in amount of 0.2 to 2 wt. % with respect to final obtained amount of modified polytetrafluoroethylene, wherein the amount of the perfluoroalkylethylene used is from 120 to 3000 ppm (by weight) based on the final obtained amount of the modified polytetrafluoroethylene, when initiating the emulsion polymerisation, the presence of the entire amount of perfluoroalkylethylene, and the polymerisation initiator used is either one or both combinations of a combination of bromate and bisulphite or sulphite and a combination of permanganate and oxalic acid: CH2= CH-Rf (1), where Rf is C1-6 a perfluoroalkyl group, wherein the polymerisation initiator is added such that either the reducing or oxidising reagent is previously present in the polymerisation reaction system, and then adding another reagent continuously or intermittently, reducing reagent or oxidising reagent pre-present in polymerisation reaction system, ranges from 0.01 to 0.50 mmol/l of the volume (L) of the aqueous medium loaded into the polymerisation vessel, and the concentration of the solid substance in the aqueous emulsion of the modified PTFE ranges from 10 to 45 wt. %. Method of producing fine powder of modified PTFE involves preparing an aqueous emulsion of modified PTFE particles using the method described above, coagulation of the obtained aqueous emulsion and drying the wet powder fine powder of modified PTFE, to obtain a powder with a standard specific weight of 2.130 to 2.145, where drying the wet fine powder of modified PTFE is carried out in an atmosphere containing ammonia, and drying temperature of wet powder ranges from 110 to 250 °C. Method of obtaining a stretched porous body of modified polytetrafluoroethylene involves obtaining fine powder of modified polytetrafluoroethylene by said method, extruding paste of the obtained fine powder of modified polytetrafluoroethylene to obtain an extruded rod and stretching the extruded rod.
EFFECT: obtaining a stretched porous body having excellent tensile strength, using a fluorinated surfactant for APFO substitution taking into account the effect on the environment.
7 cl, 12 ex, 1 tbl
